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  <title>Document</title>
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  <script>
    // 实现一个计数器函数，每次调用该函数返回一个递增的数字

    const createCounter = function() {
      let num = 0

      const fn = function() {
        num++
        return num
      }
      return fn
    }


    const counter = createCounter();
    console.log(counter()); // 1
    console.log(counter()); // 2
    console.log(counter()); // 3
  </script>
</body>
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